The present disclosure relates to an integrator and a delta-sigma modulator including such an integrator, and more particularly relates to a technique for improving the conversion precision.
In general, in order to increase a signal-to-noise ratio (hereinafter referred to as “SNR”) indicating the conversion precision of a continuous-time delta-sigma modulator used as an analog-to-digital (A/D) converter, it is effective to increase the amplitude of an input signal to be input to the A/D converter (the delta-sigma modulator). The maximum amplitude (which is also called a full-scale amplitude or overload level) of input that can be entered into an A/D converter is determined by a voltage range within which an operational amplifier and/or quantizer forming part of the A/D converter is allowed to perform processing. Usually, such amplitude is restricted by a supply voltage. For example, if the amplitude of an input signal supplied to the A/D converter (the delta-sigma modulator) is set to be equal to or higher than that of a supply voltage, the output of an operational amplifier forming part of the delta-sigma modulator is saturated to cause, e.g., a significant distortion of the output signal of the A/D converter (the delta-sigma modulator) or an unwanted abnormal oscillation state, which is a problem.